It was the kind of superlative to which Alex Salmond has become accustomed. From the gothic majesty of Westminster's central lobby, BBC political editor Nick Robinson described the first minister as "the canniest political operator in these isles".

Over the past months, the 57-year-old former economist and horse racing enthusiast has been crowned politician of the year by the Spectator and the Herald in Glasgow, named Briton of the year by the Times, and even earned a tweet from Rupert Murdoch as a "fellow anti-establishmentarian".

But for those who know Salmond, the fact that Robinson's praise was broadcast from Westminster at the moment on Tuesday when the Scottish and UK governments locked horns on Britain's biggest constitutional issue of modern times – the future of the UK itself – had a particular resonance. Because, paradoxically, Salmond loves Westminster.

After narrowly surviving a period of expulsion from the Scottish National party for membership of the socialist republican 79 Group within the party, the cocky and fresh-faced young leftwinger entered Westminster as MP for Banff and Buchan in 1987. Within three years, he was the SNP's leader, defeating its hierarchy's favourite, Margaret Ewing. It was on the floor of the Commons that Alexander Elliot Salmond's relish for gladiatorial debate was honed and polished.

Brought up in Linlithgow, west of Edinburgh, Salmond began life as the second of four children born to Robert Fyfe Findlay Salmond and Mary Stewart Salmond (née Milne). Both parents were civil servants. With his father he would spend long periods discussing Scottish politics, while his mother was from a Tory, more middle-class background. Salmond prizes domestic security, and married a Scottish Office civil servant in 1981 during his radical years. A full 17 years his senior, Moira Salmond rarely ventures into national political life but is very active at constituency level in and around Ellon in his Holyrood seat of Gordon. The couple have no children.

The journalist David Torrance has written the only biography, Salmond: Against the Odds. The first minister had a "very warm, loving" upbringing, he says. "He has always made a point of emphasising how ordinary it was, and from that he projects a Scottish Everyman image, the small-town boy, Church of Scotland, but not overly religious.

"Linlithgow is writ large in Salmond's mind as being typical middle Scotland. His stated aim was to position the SNP in the mainstream of Scottish political opinion, and that has been his over-riding aim ever since. [And] from that, he has always believed he would be able to achieve success for the SNP."

But many forget that Salmond is in his second term as SNP leader; in September 2000 he quit suddenly and for still inadequately explained reasons, less than 18 months after seeing the creation of a devolved parliament in Edinburgh. Salmond had taken his place among the SNP's 35 MSPs. But Torrance believes he felt beaten and demoralised at that point: "a sense he had reached the end of his shelf life".

"The media weren't quite as enthusiastic as they once were. And the more important aspect of this was that he simply didn't take to the Scottish parliament when it was set up: he promised dynamic opposition in May 1999, but completely failed to deliver that. He was listless; there was something missing from 1999 to 2000," says Torrance. "He missed Westminster enormously. He loved the Commons, ironically. He loved the atmosphere at Westminster, the clubability. He always believed debate was much more rigorous and intellectually challenging; that was where the main game was when the Scottish parliament was first set up."

And this period in Salmond's career produces the greatest evidence of his fallibility. There were two particular decisions which raised doubts about his judgment. The first was to openly attack Tony Blair's and Nato's decision to intervene militarily in Kosovo in 1999 as "unpardonable folly".From a nationalist and anti-militarist perspective, condemning Nato's bombing of Serbia may have been logically correct. Paul Henderson Scott, a friend and Scottish historian, said: "He thought the application of military force was inappropriate. [It] was an instinct against big powers throwing their weight about, like the Afghanistan war for instance." Yet from a political perspective, many saw it as a serious misjudgment. This was a humanitarian crisis, another phase in the Balkans' wars of ethnic cleansing. Salmond appeared to be siding with a brutal dictator. And many Pakistani-Scots were repelled. In the first Scottish election in 1999 they were target voters for the SNP, as it tried to dispel any sense that Scottish nationalism was just for native, ethnic Scots. Salmond was genuine about this. But seeing him failing to come to the aid of fellow Muslims in dire need in Kosovo, many again voted Labour.

At the same 1999 Scottish election, the SNP also devised under Salmond what many critics saw as one of its most disastrous campaigns, the "Penny for Scotland", the parliament having been granted modest tax-raising powers,the right to vary income tax by up to 3p in the pound.

It backfired. At one point, the SNP trailed Labour by 20 points. "That was a mistake," said Scott. "He thought he was appealing to Scottish sentiment, that the Scottish people would be enthusiastic about backing him up."

A report in the Independent from 23 April 1999 remarked that the SNP "was in a state of shock yesterday after an opinion poll showed public support plummeting. Black propaganda, a hostile press and the war in Kosovo were all blamed by anxious party officials but the deeper suspicion is that many Scots are frightened by the prospect of independence".

Salmond turned to Sir Sean Connery, the most famous SNP supporter; but the SNP lost the election and Salmond quit as leader, relinquishing his Holyrood seat in 2001 and returning, humbled, to relative anonymity on the backbenches at Westminster.

"The public perception, and one that his advisers are keen to perpetuate, is of a coldly calculating, tactical and strategic machine, and that's certainly true but there's also an aspect of Salmond's character which wings things a bit too much and often pushes things too far; that has been there ever since he was a student," Torrance argues.

There remain echoes of the darker side to his temperament: his fierce temper and his apparent arrogance. He got a reputation for "attacking the player, not the ball". There are still flashes of both now - his close aides admit that in private he can have a temper, and one often detects an underlying menace behind the charm. His braggadocio is seen as offputting for many female voters.

But the 21st-century Salmond is a much mellower, subtler and charismatic character. He re-entered frontline politics in 2005, regaining the leadership comfortably and returning to Holyrood. Changed by his absence, he rebuilt the party on the centre ground. And he went on to win a very narrow victory against Labour in the 2007 Holyrood election on a populist platform of tax cuts and investment in certain public services, particularly policing and schools.

Salmond resigned from the Commons in 2010. He is now the master of Holyrood. He leads a party and a front bench noted for its preternatural discipline and loyalty. That, along with weak opposition, allowed Salmond to sweep to power with an unprecedented majority in Holyrood last May, taking 69 seats.

Salmond's frontbench team and his back office staff are of a far higher calibre than those in the opposition. That has proved crucial. It has allowed him the space to invest significant time in putting his personal stamp on Scottish politics and policy; he does very little detailed policy work. His detractors sneer that he already pretends to be "President" Salmond.

He has not, of course, been without criticism in recent years – perhaps most significantly pertaining to the early release in 2009 of the man convicted of the Lockerbie bombing, and last year after launching incendiary attacks on Scottish judges on the UK supreme court.

Salmond, though, remains enormously popular. He displays a gift for engaging with people; a fatherly charm with some, a bonhomie and ready wit with others. When he talks to business leaders he displays impressive political and economic expertise.

"A huge chunk of Salmond's political credibility is based on his ease with the language of business and economics," notes Torrance. "Even by his own admission, he's a pretty rusty economist and RBS when he was there was pretty small compared to what it has become. But his ability to talk economics in an authoritative fashion sounds convincing."In all, it speaks to an unusual self-confidence and self-belief. Salmond is known too – it comes across often in public forums – for an air of pomposity and bluster.

Scott suggests Salmond's air of arrogance is due in part to Holyrood. Unlike at Westminster, nobody there is nearly his equal. "He's in a dominant position, nobody can really stand up to him, and that of course is a dangerous situation: it's likely to make many people a bit too arrogant and conceited if they're not careful," Scott argues. "Considering the press lavished on him, the fact he dominates the Scottish parliament effortlessly, for many people that would go to their heads. I think he has kept that in proportion."